feature/featuretags: make clientmetrics optional

Saves 57 KB

Updates #12614

Change-Id: If7eebec12b3cb30ae6264171d36a258c04b05a70
Signed-off-by: Brad Fitzpatrick <bradfitz@tailscale.com>

feature/buildfeatures/feature_clientmetrics_disabled.go

@@ -0,0 +1,13 @@
+// Copyright (c) Tailscale Inc & AUTHORS
+// SPDX-License-Identifier: BSD-3-Clause
+
+// Code generated by gen.go; DO NOT EDIT.
+
+//go:build ts_omit_clientmetrics
+
+package buildfeatures
+
+// HasClientMetrics is whether the binary was built with support for modular feature "Client metrics support".
+// Specifically, it's whether the binary was NOT built with the "ts_omit_clientmetrics" build tag.
+// It's a const so it can be used for dead code elimination.
+const HasClientMetrics = false

feature/buildfeatures/feature_clientmetrics_enabled.go

@@ -0,0 +1,13 @@
+// Copyright (c) Tailscale Inc & AUTHORS
+// SPDX-License-Identifier: BSD-3-Clause
+
+// Code generated by gen.go; DO NOT EDIT.
+
+//go:build !ts_omit_clientmetrics
+
+package buildfeatures
+
+// HasClientMetrics is whether the binary was built with support for modular feature "Client metrics support".
+// Specifically, it's whether the binary was NOT built with the "ts_omit_clientmetrics" build tag.
+// It's a const so it can be used for dead code elimination.
+const HasClientMetrics = true

feature/featuretags/featuretags.go

@@ -97,6 +97,7 @@ var Features = map[FeatureTag]FeatureMeta{
 	"cloud":         {Sym: "Cloud", Desc: "detect cloud environment to learn instances IPs and DNS servers"},
 	"cli":           {Sym: "CLI", Desc: "embed the CLI into the tailscaled binary"},
 	"cliconndiag":   {Sym: "CLIConnDiag", Desc: "CLI connection error diagnostics"},
+	"clientmetrics": {Sym: "ClientMetrics", Desc: "Client metrics support"},
 	"clientupdate":  {Sym: "ClientUpdate", Desc: "Client auto-update support"},
 	"completion":    {Sym: "Completion", Desc: "CLI shell completion"},
 	"dbus":          {Sym: "DBus", Desc: "Linux DBus support"},

ipn/localapi/localapi.go

@@ -1218,6 +1218,11 @@ func (h *Handler) serveHandlePushMessage(w http.ResponseWriter, r *http.Request)
 }
 
 func (h *Handler) serveUploadClientMetrics(w http.ResponseWriter, r *http.Request) {
+	if !buildfeatures.HasClientMetrics {
+		w.Header().Set("Content-Type", "application/json")
+		json.NewEncoder(w).Encode(struct{}{})
+		return
+	}
 	if r.Method != httpm.POST {
 		http.Error(w, "unsupported method", http.StatusMethodNotAllowed)
 		return

util/clientmetric/clientmetric.go

@@ -1,6 +1,8 @@
 // Copyright (c) Tailscale Inc & AUTHORS
 // SPDX-License-Identifier: BSD-3-Clause
 
+//go:build !ts_omit_clientmetrics
+
 // Package clientmetric provides client-side metrics whose values
 // get occasionally logged.
 package clientmetric

util/clientmetric/omit.go

@@ -0,0 +1,24 @@
+// Copyright (c) Tailscale Inc & AUTHORS
+// SPDX-License-Identifier: BSD-3-Clause
+
+//go:build ts_omit_clientmetrics
+
+package clientmetric
+
+type Metric struct{}
+
+func (*Metric) Add(int64)              {}
+func (*Metric) Set(int64)              {}
+func (*Metric) Value() int64           { return 0 }
+func (*Metric) Register(expvarInt any) {}
+func (*Metric) UnregisterAll()         {}
+
+func HasPublished(string) bool            { panic("unreachable") }
+func EncodeLogTailMetricsDelta() string   { return "" }
+func WritePrometheusExpositionFormat(any) {}
+
+var zeroMetric Metric
+
+func NewCounter(string) *Metric          { return &zeroMetric }
+func NewGauge(string) *Metric            { return &zeroMetric }
+func NewAggregateCounter(string) *Metric { return &zeroMetric }